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Neuroscience > chapter 5 > Flashcards

chapter 5 Flashcards

1
Q

gap junctions

A

where electrical synapses occur. interconnect non neural cells like smooth cardiac muscle, liver and glia

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2
Q

connexins

A

proteins that make up gap junction

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3
Q

connexon

A

made from 6 connexin sub units

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4
Q

how many connexons form a gap junction channel

A

2

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5
Q

difference between electrical and chemical synapse

A

electrical are faster

pore of gap junction is larger

electrical synapse is bidirectional

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6
Q

step after incoming signal depolarizes membrane above threshold, travels down axon and then reaches the axon terminal

A

synaptic transmission

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7
Q

synapse

A

a specialized junction where one part of a neuron contacts and communicates with another neuron or cell type

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8
Q

what does it mean to be electrically coupled

A

cells that are connected by a gap junction

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9
Q

in electrical synapses, can the first neuron have a PSP induced by the second?

A

yes, they are bidirectional

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10
Q

where are electrical synapses often found in the brain

A

where normal function requires that the activity of neighboring neurons is highly synced

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11
Q

inferior olive

A

neurons in brain step nucleus that can generate small oscillations of membrane voltage and action potentials. they send axons to cerebellum and are important in motor control

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12
Q

when are gap junctions prominent?

A

early in development. it helps with growth and maturation

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13
Q

synaptic cleft

A

what pre and post synaptic membranes are separated by in chemical synapse

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14
Q

what is the synaptic cleft filled with?

A

extracellular protein. it serves as a “glue” that binds membranes together

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15
Q

what is usually the presynaptic element

A

axon terminal

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16
Q

synaptic vesicle

A

stores neurotransmitters

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17
Q

secretory granule

A

larger vesicles that contain soluble protein. also called dense-core vesicle since it appears dark

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18
Q

membrane differentiations

A

accumulation of protein adjacent to and within membranes on EITHER SIDE of synaptic cleft

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19
Q

active zones

A

actual sites of NT release

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20
Q

where are synaptic vesicles clustered?

A

cytoplasm adjacent to active zone

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21
Q

post synaptic density

A

protein thickly accumulated in and under postsynaptic membrane. contains NT receptors

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22
Q

what do neurotransmitter receptors do?

A

convert intercellular chemical signal to an intracellular chemical signal

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23
Q

if a post synaptic membrane is a dendrite

A

axodendritic

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24
Q

is a postsynaptic membrane is a cell body

A

axosomatic

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25
Q

when presynaptic membrane is on another axon

A

axoaxonic

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26
Q

when presynaptic axon is on a postsynaptic dendritic spine

A

axospinous

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27
Q

dendrodendritic

A

when its a dendrite/dendrite synapse. only happens in specialized neurons

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28
Q

grays type I

A

asymmetric post synaptic side is thicker. its also called asymmetrical synapses

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29
Q

is grays type I usually excitatory or inhibitory

A

excitatory

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30
Q

grays type II

A

symetrical. usually inhibitory

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31
Q

neuromuscular junction

A

chemical synapses that occur between axons of motor neurons of spinal chord and skeletal muscle

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32
Q

what always happens in neuromuscular junction?

A

action potential in motor axon always causes action potential in muscle cell it innervates

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33
Q

what has the largest synapse in the body?

A

neuromuscular junction

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34
Q

motor end plate

A

contains series of shallow folds in neuromuscular junction. also called post synaptic membrane

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35
Q

structure of motor end plate

A

folds of post synaptic membranes are packed with receptors

presynaptic active zones are aligned precisely with junctional folds

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36
Q

why are neuromuscular junctional folds inportant

A

ensures that many neurotransmitters are released onto a large surface of chemically sensitive membrane

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37
Q

what do amino acids and amines contain?

A

at least one nitrogen atom

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38
Q

where are amino acids and amines stored and released

A

synaptic vesicles

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39
Q

where are peptides stored and released

A

from the large secretory granules. this is because they are large molecules (chains of amino acids)

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40
Q

what are most CNS synapses usually mediated by?

A

amino acids

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41
Q

what mediates fast synaptic transmission at all neuromuscular junctions?

A

ACh

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42
Q

gaba is made primarily by…

A

the neurons that release them

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43
Q

what concentrates NTs inside vesicle?

A

transporter proteins

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44
Q

where are transporter proteins located

A

in vesicle membrane

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45
Q

peptides are formed when…

A

amino acids are strung together by ribosomes of cell body. occurs in rough ER

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46
Q

steps of peptide synthesis

A

peptide synthesized in rough ER

chain split in golgi apparatus- one of the smaller fragments is NT

secretory granules containing peptide bud off from golgi apparatus

secretory grandules transport down axon to terminal where peptide is stored

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47
Q

steps of amine and amino acid synthesis

A

enzymes connect precursor molecule into NT molecule in cytosol

transporter proteins load the NT inyo synaptic vesicle where they are stored

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48
Q

where are voltage gated calcium channels located

A

in active zone

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49
Q

why will Ca2+ flood into cytoplasm as long as they are open?

A

resting calcium concentration is low….0.0002 mM

50
Q

exocytosis

A

when synaptic vesicle fuses to presynaptic membrane @active zone allowing contents of vesicle to spill out into synaptic cleft

51
Q

steps of exocytosis

A

synaptic vesicle is loaded with NT

influx of Ca2+ through channel

release of contents into cleft by fusion of vesicle membrane

eventually recycled by process of endocytosis

52
Q

endocytosis

A

when vesicle membrane is recovered and recycled vesicle is refilled with NT

53
Q

what happens during prolonged periods of stimulation?

A

vesicles are mobilized from a “rescue pool” that is bound to cytoskeleton of axon terminal. release is triggered by elevations of Ca2+

54
Q

step one of chemical synapse (synthesis)

A

some NT are transported from cell nucleus to terminal buttons…others are made from building blocks imported into the terminal, they are packaged into vesicles there

55
Q

step two of chemical synapse (release)

A

in response to an action potential, the neurotransmitter is released across the membrane by exocytosis

56
Q

step three of chemical synapse (receptor action)

A

the transmitter crosses the synaptic cleft and binds to a receptor

57
Q

step four of chemical synapse (inactivation)

A

the transmitter is either taken back into the terminal or inactivated in the synaptic cleft

58
Q

why are peptides not released in response to every action potential

A

sites of grandual exocytosis occur at a distance from Ca2+ entry. release requires high frequency trains of action potentials so that Ca2+ throughout the terminal can build to the level required to trigger release away from active zones. takes longer

59
Q

are peptides released in active zones

A

no

60
Q

post synaptic density

A

protein dense specialization attached to post synaptic membrane

61
Q

neurotransmitters affect the postsynaptic neuron by…

A

binding to specific receptor proteins in the post synaptic density

62
Q

what are the two types of NT receptors?

A

transmitter gated ion channels

g-protein coupled receptors

63
Q

in transmitter gated ion channels, what happens when NT binds to specific site on extracellular region?

A

slight twist of subunits which causes the pore to open

64
Q

how many subunits make a channel

A

4-5

65
Q

what channel does not show much ion selectivity?

A

transmitter gated ion channel ex Ach gated channel is permeable to both Na+ and K+

66
Q

ionotropic

A

acts quickly. ionic receptors change shape when bound by a ligand.

this channel changes shape to allow ions to flow through

67
Q

metabotropic action

A

takes longer depending on the number of steps required to produce a response

they do not have channels

activate g-protein that in turn activates a secondary messenger, that in turn will activate something else

68
Q

when is channel classified as excitatory?

A

if it is permeable to Na+

69
Q

excitatory post synaptic potential

A

transient post synaptic depolarization caused by presynaptic release of NT

70
Q

when is channel inhibatory

A

if it is permeable to Cl-, it hyperpolarizes postsynaptic cell from resting membrane potential

71
Q

steps of g-protein coupled receptors

A

NT binds to receptor proteins in post synaptic membrane

receptor proteins activate g-proteins which are free to move along the intracellular face of the post synaptic membrane

activated g-proteins activate “effector” proteins

72
Q

what makes g-protein receptors special?

A

they have seven transmembrane alpha helices

73
Q

what does it mean that g-protein receptors have seven transmembrane alpha helices

A

they span the membrane seven times

74
Q

g-proteins have the ability to bind…

A

GTP and GDP

guanosine triphosphate and guanosine diphosphate

75
Q

example of ionotropic receptor

A

nicotinic receptor at neuromuscular junction

76
Q

example of metabotropic

A

acetylcholine at neuromuscular junction (longer lasting)

77
Q

what can effector proteins be?

A

g-protein gated ion channels in the membrane or enzymes that synthesize molecules called second messengers that diffuse away in cytosol

78
Q

what else can g-protein receptors be referred to?

A

metabotropic receptors because they trigger widespread metabolic effects

79
Q

the same NT can have different effects based off of….

A

what kind of receptor it binds to

80
Q

autoreceptor

A

presynaptic receptors that are sensitive to neurotransmitter released. it acts as a safety valve to reduce release when NT gets too high

81
Q

what allows a pre synaptic terminal to regulate itself?

A

autoreceptors

82
Q

autoreceptors are usually…

A

g protein coupled receptors and a common dffect is inhibition of NT release or synthesis

83
Q

what happens after NT release?

A

reuptake into presynaptic terminal

enzymatical degradation and recycled

84
Q

glial cells help with NT removal by..

A

containing NT transporters

85
Q

how is ACh terminated from neuromuscular junction

A

enzamatic destruction happens in cleft itself

86
Q

what happens if transmitter removal sucks? (from drugs n shit)

A

desensitization despite continued presence of NT, channels will stay closed

87
Q

neuropharmacology

A

the study of the effect of drugs on nervous system tissue

88
Q

inhibitors

A

drugs that inhibit normal function of specific proteins involved in synaptic transmission

89
Q

receptor antagonist

A

inhibitors of T receptors that bind to receptors and block (antagonize) the normal action of the transmitter

90
Q

receptor agonist

A

drugs that mimic the actions of the naturally occuring neurotransmitter

91
Q

nicotinic ACh receptors

A

located in muscles and uses this name to distinguish them from other types

92
Q

what ACh receptors are involved with addictive effects of tobacco use

A

nicotinic receptors in the CNS

93
Q

what do second messengers do?

A

activate additional enzymes in the cytosol that can regulate ion channel function and alter cellular metabolism

94
Q

ACh effect on heart

A

slows rhythm of contractions by causing slow hyperpolarization of cardiac muscle cells.

metabotropic ACh receptor is coupled by g-protein to a potassium channel

opening of k channel hyperpolarizes cardiac muscle fibers and reduces the rate at which it fires action potentials

95
Q

ACh effect on skeletal muscles

A

induces contraction by depolarizing muscle fibers.

receptor is a transmitter gated ion channel, specifically ACh channel permeable to Na..opening of this channel depolarizes the muscle fibers and makes them more excitable

96
Q

generation of ISPS steps

A

action potential arriving in the presynaptic terminal causes the release of neurotransmitter

molecules bind to transmitter gated ion channel in post synaptic membrane..if Cl- enters postsynaptic cell through open channel, membrane will become hyper-polarized

97
Q

binding of NT to receptor leads to activation of g-proteins.

activated g-proteins activate effector proteins which may be..

A

ion channels or

enzymes that generate intracellular second messenger

98
Q

what is the elementary unit of neurotransmitter release

A

epsp

99
Q

how many transmitter gated channels are activated depend on….

A

how much NT is released

100
Q

the amplitude of EPSP is based on…

A

the number of transmitter molecules in a single synaptic vesicle

number of post synaptic receptors available at the synapse

101
Q

why is there a difference between EPSP at neuromuscular junction and CNS

A

neuromuscular junction has to ensure that it is fail safe and generates EPSP at a huge size.

if every EPSP can capable of generating action potential in post synaptic cell, then a neuron would be little more than a relay situation. it needs to preform more sophisticated computations

102
Q

what is integration of EPSP

A

many EPSP add together to produce significant post synaptic depolarization

103
Q

spatial summation

A

adding together of EPSP generated simultaneously at many different synapses at the dendrite

104
Q

temporal summation

A

adding together of EPSP

105
Q

temporal summation

A

adding together of epsp generated at the same synapse

106
Q

what does the effectiveness of EPSP triggering action potential depend on

A

how far the synapse is from the spike initiation zone

properties of dendritic membrane

107
Q

miniature post synaptic potential

A

generated by transmitter contents of one of the vesicles in ABSENCE of an action potential

108
Q

what two paths can synaptic current take

A

down inside dendrite

across the membrane

109
Q

how do dendritic cable properties contribute to synaptic integration

A

internal resistance depends on diameter of dendrite

as current proceeds down the dendrite and to the synapse, the esps amplitude will deminish bc of the leakage of ionic currents through membrane channels

110
Q

length constant

A

where depolarization is about 37% of that at the orgin.

111
Q

when will an esps be more likely generated

A

if it has a longer length constant

112
Q

internal resistance

A

resistance to current flowing longatudially

113
Q

membrane resistance

A

resistance to current flowing across the membrane

114
Q

what does internal resistance depend on

A

diameter of the dendrite and electrical properties of cytoplasm

115
Q

what does membrane resistance depend on

A

of open ion channels

116
Q

voltage gated channels in dendrites can act as important amplifiers of..

A

small PSP generated far out on dendrites

117
Q

inhibitory synapse

A

job is to take the membrane away from action potential threshold. they exert a powerful control over a neurons output

118
Q

what NTs bind to inhibitory synapse

A

GABA and glycine

119
Q

similarities and difference between inhibitory snapse and excitatory snypse

A

both use transmitter gated ion channels

inhibitory is only permeable to Cl-

120
Q

what is shunting inhibition

A

when snypse acts as an electrical shunt and prevents current from flowing through soma to axon hillock

121
Q

where are inhibitory snypses clustered

A

on soma or near axon hillox

Neuroscience (20 decks)

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